On-chip voltage regulation is a challenge in integrated circuits (ICs). Low-dropout (LDO) voltage regulators create a custom, stepped-down voltage inside of an IC. They must remain stable while adapting to varying load currents and reducing the amount of noise at the output. The dropout voltage is the minimum voltage required across the regulator to maintain regulation. One common use for a voltage regulator is to provide a low-noise, custom voltage for a phase-locked loop (PLL). Modern communication protocols have very stringent specifications on PLLs, which rely on good voltage regulation to share some of the burden of satisfying these specifications. Beyond low noise generation across significant load variation, a good voltage regulator provides high power supply rejection (PSRR), so that the output voltage remains constant across a broad range of input voltages. In addition, the regulator should be energy efficient—ideally, consuming no power itself. Finally, process, voltage, and temperature (PVT) variation will change the performance of the transistors in ICs. The regulator design must be robust to these sources of variation.